[RogerBW]

Production at solar-powered factories. I found it necessary to have dV in the 100mps+ range in order to get useful travel times, particularly for multi-system trips (enter the system at a jump point, cross it to get to the next jump point). Fusion rockets look tempting, but the low thrust means it doesn't matter how much dV you have, you don't have time to use it.

It's a setting assumption that getting a boom rather than a prolonged fizzle out of antimatter takes work. (The energy release tends to push the reacting surfaces apart. This is the best current theory I could find while working on Meltdown and Fallout.)